Actinopterygii

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Actinopterygii ( ), or finned fish , is a class or subclass of bony fish.

These finned fish are so called because their fin is a skin net supported by the spine or spine ("rays"), as opposed to a fleshy fins, which marks the Sarcopterygii class (lobe finned fish). This actinopterygian fin rays attach directly to the proximal or basal, radial skeletal element, which represents the connection or relationship between these fins and the internal frame (eg, pelvis and pectoral girdle).

Numerically, actinopterygians are the dominant class of vertebrates, comprising nearly 99% of over 30,000 species of fish. They are everywhere in all freshwater and marine environments from the deep sea to the highest mountains. The remaining species may vary in size from Paedocypris <8, at 8 mm (0.3 inches), on massive ocean sunfish, at 2,300 kg (5,070 pounds), and long-bodied oarfish, at 11 m (36Ã , Ft).

Video Actinopterygii

Characteristics

The finned fish appears in various shapes. The main features of the typical finned fish are shown in the adjacent diagrams.

Maps Actinopterygii

Reproduction

In almost all ray-finned fish, the sexes are separate, and in most female species spawn an externally fertilized egg, usually with male egg insemination after they are laid. Development is then continued with the free-swimming larvae stage. Yet another ontogeny pattern exists, with one of the most common sequential hermaphroditisms. In most cases this involves protogini, the early life of fish as females and conversion to males at some stage, triggered by some internal or external factors. Protandry, in which fish convert from male to female, is much more common than protogini. Most families use external fertilization rather than internal fertilization. Of oviparous teleosts, most (79%) do not provide parental care. Viviparity, ovoviviparity, or some form of parental care for eggs, either by men, women, or both parents seen in a significant fraction (21%) of 422 teleost families; no possible treatment is the condition of the ancestors. Viviparity is relatively rare and is found in about 6% of teleost species; men's care is much more common than women's care. The male area of ​​"preadapts" is a species for the care of parents who evolved.

There are several examples of self-fertilizing fish. The mangrove rivulus is a hermaphrodite, a simultaneous amphibian, producing eggs and laying eggs and has an internal fertilization. This mode of reproduction may be related to the long time consuming fish habit of getting out of the water in the inhabited mangroves. Men are sometimes produced at temperatures below 19 ° C (66 ° F) and can fertilize the eggs that are then delivered by females. It maintains genetic variability in a species that is otherwise highly inbred.

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Fossil record

The earliest known fossil actinopterygiian is Andreolepis hedei , derived from 420 million years (End of Siluria). Remnants are found in Russia, Sweden, and Estonia.

src: www.fossilmuseum.net

Classification

Actinopterygians are divided into subclasses of Chondrostei and Neopterygii. Neopterygii, in turn, is divided into the infraclasses of Holostei and Teleostei. During Mesozoic and Kenozoic teleosts are particularly diversified extensively, and as a result, 96% of all known fish species are teleosts. Cladogram shows the main group of actinopterygians and their relationship to terrestrial vertebrates (tetrapods) that evolved from the associated fish groups. Estimated dates are from Near et al., 2012.

Polypterids (bichir and ropefish) are the siblings of all other actinopterygians, The Acipenseriformes (sturgeons and paddlefishes) are the sisters of Neopterygii's brother, and Holostei (bowfin and gars) are the lineage of siblings. Elopomorpha (eel and tarpon) seems to be the most basic teleost.

Source of the article : Wikipedia